1. Field of the Invention
This invention relates to a device for cropping and deflecting a wire-rod strand moving at high speed, in which the strand is forcibly guided through a switch tube between two cutter heads arranged on top of each other and equipped with a cutter each, so that a head end of the strand that does not meet quality requirements is separated from the strand, whereas the separated crop end and the sound wire-rod strand are passed into a down stream outlet section comprising separated guide channels.
2. The Prior Art
It is known to crop or divide a wire-rod strand moving at mill speed in rolling mills for improving the entry conditions for the initial pass in the roll stands downstream, or in order to cut off parts of the strand that fail to meet quality requirements, and to dispose of these parts as scrap.
Adapted to the high rolling speeds of the strand is, e.g., cropped or divided by flying shears such as shown in European patent No. EP 0 297 313 B1 and German patent No. DE 35 23 046 A1.
With their high speeds and with the minimum switching time periods required for switches downstream, these shears are necessarily highly complicated mechanical systems. High driving powers are required for accelerating the associated switch systems and the cutters, and the components of the switches are subject to considerable wear. Because of rolling speeds in excess of 100 m/s and due to the high forces of acceleration, it is technically difficult to control these systems, and a high technical effort is needed to manage their operation.
In practical applications, the switch systems are made very long in order to achieve appropriate switching timer periods for the switches.
DD 145 237 discloses designing the outlet part, which consists of a plurality of guide channels, in such a way that it can be swung horizontally. The wire-rod strand is then guided to machines arranged downstream, or the separated ends are admitted to a suitable scrap disposal installation. A linear drive controls the swinging.
However, also this measure fails to satisfactorily solve the problem of short swinging time periods amounting to 1/10th of a second.
Furthermore, German Patent Application No. DE 32 37 171 A1 discloses a guiding system comprising a segment-like deflector for deflecting the wire-rod strand, whereby the deflector is brought into contact with the wire-rod strand in order to deflect it into the appropriate guide channels. This device has the drawback that due to the fact that the strand is in direct contact with the deflector, the possibility of swerving of the strand moving at high speeds, which may cause damage, cannot be absolutely excluded.
A different solution to the problem of short switching time periods for downstream switch systems has been proposed by DD 218 852 in which the cropped piece of strand and the sound wire-rod strand are guided into various guide channels after the separation cut has been made. The device operates in such a way that in the course of the dividing process, the cropped piece of strand is pressed down by the leading top cutter, and the following head of the sound strand being rolled is lifted by the trailing bottom cutter. This measure supports the movement of the piece of scrap into the downwardly arranged channel of the outlet section, as well as the movement of the following sound strand into the wire-rod strand channel arranged on top. The cutter heads are designed so that starting from the center breast area of the cutter, the diameter of the cutter head expands toward the opposite back side of the cutter and ends at the level of the top edge of the cutter.
This device appears to be suitable to accommodate the high rolling speeds. However, the specific cutter heads required are very expensive to design and manufacture. Furthermore, the effect of deflection of the strand depends also on the steel grade and upon the rolling conditions. Thus, the desired deflection is therefore not always achieved reliably, because forced guidance of the strand after is has been cut is missing.